Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 40 years ago and resembles a phonograph. That is, the hard drive model includes a plurality of storage disks or hard disks vertically aligned about a central core that spin at a standard rotational speed. A plurality of magnetic read/write transducer heads, for example, one head per surface of a disk, is mounted on the actuator arm. The actuator arm is utilized to reach out over the disk to or from a location on the disk where information is stored. The complete assembly, e.g., the arm and head, is known as a head gimbal assembly (HGA).
In operation, the plurality of hard disks is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are channels or tracks evenly spaced at known intervals across the disks. When a request for a read of a specific portion or track is received, the hard disk drive aligns a head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk drive aligns a head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, refinements of the disk and the head have provided great reductions in the size of the hard disk drive. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are generally much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Refinements also include the use of smaller components and laser advances within the head portion. That is, by reducing the read/write tolerances of the head portion, the tracks on the disk can be reduced in size by the same margin. Thus, as modern laser and other micro recognition technology are applied to the head, the track size on the disk can be further compressed.
A second refinement to the hard disk drive is the increased efficiency and reduced size of the spindle motor spinning the disk. That is, as technology has reduced motor size and power draw for small motors, the mechanical portion of the hard disk drive can be reduced and additional revolutions per minute (RPM) can be achieved. For example, it is not uncommon for a hard disk drive to reach speeds of 15,000 RPM. This second refinement provides weight and size reductions to the hard disk drive and increases the linear density of information per track. Increased rates of revolution also provide a faster read and write rate for the disk and decrease the latency, or time required for a data area to become located beneath a head, thereby providing increased speed for accessing data. The increase in data acquisition speed due to the increased RPM of the disk drive and the more efficient read/write head portion provide modern computers with hard disk speed and storage capabilities that are continually increasing.
A wafer is a basic “building block” upon which numerous processing actions take place to produce semiconductor devices. Wafers also form a similar building block for the production of magnetic read and/or write heads and disks as used in hard disk drives. The production of such devices can comprise many different processing steps. It is not uncommon for hundreds of operations to be performed on wafers. Frequently, such production processes require that wafers be moved from one machine to another. Generally, wafers are grouped together for such transport between machines or storage. Wafers are typically moved among a variety of wafer processing equipment in carriers known as cassettes. Sometimes such a cassette is also known as a “boat.”
A cassette is generally constructed from an engineering plastic. It typically comprises a plurality of slots that support and isolate each wafer. A cassette may hold up to about two dozen wafers, sometimes more. Although there are a variety of styles of cassettes available from a variety of manufacturers, a cassette is typically closed on top and bottom surfaces and closed on three sides. A fourth side is typically open, allowing for individual wafers to be moved in and out of the cassette by wafer processing equipment.
Cassettes are typically hand carried into an acceptance port of wafer processing equipment. Frequently, such an acceptance port can comprise an elevator that lowers the cassette into the wafer processing equipment for automated processing. Generally, a robotic arm grasps a single wafer, removes the wafer from the cassette and places the wafer into a load station of the wafer processing equipment for processing.
Unfortunately, wafers sometimes do not maintain a desired alignment within a cassette. For example, various handling operations, e.g., a “bump,” of a cassette can dislodge one or more wafers from their desired position within the cassette. In addition, errors by automated wafer handling equipment can sometimes incorrectly place a wafer into a cassette. Further, robotic arms can incorrectly position wafers within the wafer processing equipment, e.g., a load station. For example, a wafer can have an unexpected adhesion to a robotic arm. When released from the robotic arm, such an adhesion can cause a wafer to fall into an incorrect position within the wafer processing equipment.
Such misaligned wafers can frequently cause a processing disruption at a subsequent processing stage. For example, a wafer that is misaligned in a cassette can be incorrectly accessed by a robotic arm. Such an incorrect access can result in incorrect placement of a wafer within the processing device. Alternatively, various positioning errors can result due to a transfer from a wafer carrier to the wafer processing equipment. Typically, after a time-out interval, the processing device will detect the incorrect placement of the wafer and reject that wafer. A common response to such a situation stops production flow and requires manual intervention to restore normal production. Manual intervention is not only costly in terms of direct costs and production delays, but further has the potential to introduce deleterious contamination onto the wafer and/or into the processing equipment. Contamination thus introduced can result in defects that have a detrimental effect upon production yield. In some cases, such defects may not be detected until much later in a production process.
Accordingly, there is a need for systems and methods for aligning wafers within wafer processing equipment. Additionally, in conjunction with the aforementioned need, systems and methods for automatically aligning wafers within wafer processing equipment while minimizing contamination opportunities and rinsing wafers are desired. A further need, in conjunction with the aforementioned needs, is for aligning wafers within wafer processing equipment in a manner that is compatible and complimentary with existing wafer processing systems and manufacturing processes.